####018008203####
FXUS66 KMFR 260320

AFDMFR



Area Forecast Discussion

National Weather Service Medford OR

820 PM PDT Thu Apr 25 2024



.DISCUSSION...Another wave is moving onshore, which will bring

behind it the bulk of the moisture from this system. The timing 

and intensity looks in line with the current forecast, so no 

changes were made. Friday morning snow levels still look to be at 

their lowest point, in the 4700 to 5200 foot range. However, snow 

related impacts should be very minimal because so far road 

temperatures have proven to be quite warm with snow melting on 

contact. Overnight temperatures will also continue to fall over 

the next 48 hours, so be sure to check your local forecast in the 

event you have any gardening related concerns. 



&&



.AVIATION...(25/00Z TAFs)... MVFR ceilings are expected to continue 

along the coast through this TAF cycle and likely overnight, too. 

For all other areas, VFR will be the more dominate category through 

this cycle. Rainfall could bring ceilings down to MVFR, but the 

region will move into a few hour lull in activity, before another 

wave move onshore around 6z. Cloud cover continue to cause mountain 

obstructions across the region, too. Winds have been gusting between 

20 and 30 kt this afternoon and it is expected for them to lower 

before the start of the 06z TAF cycle. Friday afternoon though, 

winds at least east of the Cascades are expected to become gusty 

again.

-Miles



&&



.MARINE...Updated 800 PM Thursday, April 25, 2024...A front is

moving inland this evening. Behind the front, breezy to gusty west 

to southwest winds and steep fresh seas will continue tonight into 

Friday. While wind speeds gradually diminish late Friday afternoon 

and evening, steep west swell will result in seas hazardous to small 

craft. These conditions are likely to last into late Friday night. 

By Saturday afternoon, another front will push into the area, and 

seas may become chaotic once again into Saturday evening. 

Additionally, we are going into a rainy pattern with chances over 

the waters nearly every day in the forecast through middle next 

week.  



-CC



&&



.PREV DISCUSSION... /Issued 453 PM PDT Thu Apr 25 2024/ 



DISCUSSION...



Short Term...Tonight through Saturday Night...Currently,

widespread showers cover much of southern Oregon and far northern

California, with snow levels currently around 6000 feet. Shower

activity will continue through this evening, then will reintensify

as the upper level trough axis swings overhead tonight and tomorrow.

As this occurs, snow levels will lower to 5000 feet, and snowfall

rates will peak between roughly 2 AM through midday Friday. 

Amounts of 5 to 12 inches are forecast with highest amounts for 

the back country and highest elevations. Recent warmth is sure to

limit amounts on roadways, but at the very least those traveling 

around Crater Lake, Diamond Lake, and Willamette Pass should be 

prepared for reduced visibilities. The highest peaks of the 

Siskiyou Mountains, Warner Mountains, and Siskiyou County can also

expect to receive measureable accumulations.



Precipitation will taper off Friday evening into Friday night, 

then after a short break Saturday morning as weak ridging passes 

overhead, the next shortwave arrives Saturday. This will be a 

quick moving and somewhat weak wave, but it will be the leading 

edge of sustained zonal onshore flow that will persist through at 

least Saturday night. This pattern is known to produce ongoing 

light showers, and this is no exception, although most 

precipitation will remain confined mainly along and west of the 

Cascades. Snow levels are expected to remain fairly consistent, 

throughout this time, hovering roughly around 5000 feet. 



Temperatures throughout the short term will remain right around 

normal for this time of year. -BPN 



LONG TERM...Sunday morning through Thursday night.



This cool unsettled flow will continue into Sunday with the best 

chance of precipitation west of the Cascades and within Oregon. 

However, locations east of the Cascades and in northern California 

are anticipated to be dry.  This is most likely due to weak forcing 

and a lack of moisture farther to the south under this zonal flow. 

This synoptic pattern will likely continue into Monday as short 

waves move through this zonal flow.



Heading into Tuesday,  500 mb heights appear more zonal over Oregon 

as another short wave swings through the state of Washington.  This 

appears to be the driest day as the chance of rain is generally 

below 15% everywhere except along the coast near Cape Blanco and Coos 

Bay. Given this drier trend, temperatures should push into the 70's 

in Medford, Grants pass and the upper 60's in other locations across 

our forecast area.



Eventually, an upper level low out of the Gulf of Alaska will likely 

push into the Pacific Northwest around Wednesday. This should result 

in another round of wetting rain, although the NBM probability of 

precipitation of 0.01 inches over 12 hours only show a 50 to 60% 

chance of rain. Therefore, some of the ensemble members might show 

different times of arrival of the front on Wednesday night and 

Thursday morning or it is drier than what some of the deterministic 

data show. 



The other thing that this low will bring is some cooler more 

unstable air behind the cold front. This can be seen in the snow 

levels falling down to 4000 feet behind the front, which should 

eventually pass through sometime around Thursday.  Even with plenty 

of solar heating, high temperatures are still anticipated to push 

into the lower 60's in many cities east and west of the Cascades.



Overall, the extended forecast looks active yet with little to no 

impacts. We're lacking significant moisture or forcing to bring 

impactful rain or snow to the region. One may say it is very Spring 

like for our forecast area.



-Smith



AVIATION (25/00Z TAFs)...

MVFR ceilings are expected to continue along the coast through this 

TAF cycle and likely overnight, too. For all other areas, VFR will 

be the more dominate category through this cycle. Rainfall could 

bring ceilings down to MVFR, but the region will move into a few 

hour lull in activity, before another wave move onshore around 

6z. Cloud cover continue to cause mountain obstructions across the

region, too. Winds have been gusting between 20 and 30 kt this 

afternoon and it is expected for them to lower before the start of

the 06z TAF cycle. Friday afternoon though, winds at least east 

of the Cascades are expected to become gusty again.

-Miles



MARINE...Updated 200 PM Thursday, April 25, 2024...A small craft 

advisory remains in effect for all of the waters as a front 

continues to make its way onshore today. The northern waters will 

experience the strongest wind speeds with a couple isolated areas 

perhaps seeing gales this afternoon. The front also brought 

widespread rainfall to the area earlier today, but rainfall over the 

waters has diminished quite a bit. In fact, satellite is indicating 

some clearing in our western waters, and we are likely to see a lull 

in activity over the waters until later tonight into Friday morning 

when the next round of rainfall is anticipated. 



While wind speeds diminish tomorrow, swell remains over the waters 

and will keep seas hazardous to small craft. These conditions are 

likely to last into Saturday morning. By Saturday afternoon, another 

front will push into the area, and seas may become chaotic once 

again. Additionally, we are going into a rainy pattern with chances 

over the waters nearly every day in the forecast through middle next 

week. 



&&



.MFR WATCHES/WARNINGS/ADVISORIES...

OR...Winter Weather Advisory until 2 PM PDT Friday above 5000 feet 

     for ORZ027-028.



CA...None.



PACIFIC COASTAL WATERS...Small Craft Advisory until 2 AM PDT Saturday 

     for PZZ350-356-370-376. 



&&



$$

####018007334####
FXUS63 KILX 260325

AFDILX



Area Forecast Discussion...Updated Aviation

National Weather Service Lincoln IL

1025 PM CDT Thu Apr 25 2024



.KEY MESSAGES...

 

- There will be multiple rounds of showers and storms Friday

  through the weekend. Some of the storms could be severe each day

  (5-15%). Much of the area west of I-57 can expect 1-2 inches of

  rain (50th percentile) through Monday morning, but localized

  amounts in excess of 3 inches (90th percentile) are possible

  particularly north of the Illinois River.



- Warm and windy conditions are expected this weekend. Daily highs

  will be near or into the 80s accompanied by breezy southerly

  winds gusting 30 to 40mph.



&&



.UPDATE...

Issued at 844 PM CDT Thu Apr 25 2024



Latest regional radar mosaic indicated a band of showers and

embedded thunderstorms stretched from northeast KS southeast into

western TN, located in a zone of elevated warm advection. This

lift and associated area of precip will shift northeast overnight,

reaching our west central IL counties around daybreak. Instability

will be much diminished by then, so mainly expecting showers with

an isolated storm possible. Otherwise most of the overnight will

remain dry with thickening high and mid level clouds. East-

southeast winds to increase to 10-20 mph late as the MSLP gradient

tightens between high pressure over the eastern Great Lakes and

low pressure developing in the lee of the Colorado Rockies. These

winds and the increasing cloud thickness will keep lows several

degrees warmer than last night, mainly in the mid/upper 40s.



25



&&



.DISCUSSION...

Issued at 243 PM CDT Thu Apr 25 2024



This afternoon, low pressure is in place along the Front Range of 

the Colorado Rockies while a warm front stretches east across 

Kansas into southern Missouri. This low and attendant warm front 

will lift northeast tonight while a broad low level jet sets up 

across the mid Missouri Valley. Thunderstorms will expand in 

coverage in response to this feature and move east across IA/MO 

overnight and eventually expand into portions of Illinois Friday 

morning. These early day storms will outrun the stronger 

instability to the west and the forcing associated with the 

weakening/veering low level jet. As such, expect an initial round 

of showers with a few embedded non-severe storms to move across 

central Illinois through the mid/late morning and early afternoon 

hours. Additional showers and storms will be possible through the 

day as the warm front gradually lifts across central Illinois 

allowing dew points well into the 50s to overspread the area. The 

next round of strong to severe storms will initially develop 

within a narrow ribbon of moderately strong instability near the 

NE/IA state line and spread east overnight. These storms should be

in a decaying state as they cross the Mississippi River given the

unfavorable diurnal timing and as storms outrun the stronger 

instability to the west. Otherwise some elevated WAA driven storms

will be possible Friday night.



Saturday continues to look like the better day for higher impact 

severe weather potential, though this threat is conditional as 

forcing continues to be nebulous with shortwave ridging overhead 

between the two main systems. Moderate to strong instability is 

expected to develop within the warm sector across portions of the 

mid Mississippi Valley Saturday afternoon. GFS indicates that up 

to around 2000 J/kg MLCAPE will develop during the afternoon, 

strongest across portions of the Illinois River Valley. MLCIN is 

expected to be minimal with capping around or weaker than 30 J/kg.

That being said, overall synoptic scale forcing for ascent will 

also be weak, in between the departing low over the Upper Midwest 

and ahead of the second low developing across the Great Plains. If

we are able to overcome this and see convective initiation occur 

Saturday afternoon, deep layer shear of 35-40 kt will be 

sufficiently strong to support a few supercells with all severe 

hazards in play, especially west of I-55 where shear and 

instability are greatest.



Saturday evening and overnight, precip coverage will increase in 

response to a strengthening low level jet. Corfidi vectors fall 

off to 5kt or less and oppose the 850-300mb flow from NE Missouri 

into northern Illinois Saturday night. A corridor of heavy rain 

should result from both training and backbuilding storms Saturday 

night, though placement of the axis of heaviest rain may stay just

to our west or clip only our far western counties (near the 

Illinois River Valley). 12-hour 90-95th percentile QPF from the 

NBM shows the potential for around 1.00-1.75 inches of rain 

Saturday night north of the Illinois River.



Sunday, second area of low pressure is progged to lift from Kansas 

into the Upper Midwest through the day. Guidance continues to 

advertise minimal recovery during the day Sunday across central 

Illinois due to ongoing convection and cloud cover early in the 

day. GFS for example only develops around 300-700 J/kg MLCAPE by 

Sunday afternoon. Sunday night, there are indications that 

portions of central Illinois could see a minima in precip amounts 

as the area is bifurcated by the main upper low lifting across the

upper Mississippi Valley and a shortwave digging across the lower

Mississippi Valley. Still, broad warm advection across the region

will support a chance for additional showers and storms, 

especially during the evening and overnight hours. Trailing cold 

front has slowed down from earlier runs, now tracking across 

central Illinois more during the day Monday as opposed to Sunday 

night. Tail end of the front/col area slowly moves across central 

Illinois Monday afternoon and will support additional chances for 

showers and storms. Deep layer shear appears to weaken 

significantly Monday as the main upper wave lifts into Canada.



Daily chances for showers and storms continue into next week along 

with warm temperatures. A frontal boundary will push into and then

stall over the region Tuesday through Wednesday or Thursday of 

next week and will serve as the focus for additional precip. 

Expect daily highs in the 70s through this time frame.



Deubelbeiss



&&



.AVIATION...  (For the 06z TAFs through 06z Friday Night)

Issued at 1025 PM CDT Thu Apr 25 2024



High pressure over the eastern Great Lakes will shift east

tonight, as low pressure moves into the western Plains. This will

keep east-southeast winds blowing around 10-12 kt overnight, then

gust 20-25 kt on Friday when the gradient tightens. Mainly high

cirrus in place through much of tonight, then lowering cloud bases

after sunrise with the approach of a warm front. Ahead of the

front, a band of showers is likely to affect all terminals late

morning through much of the afternoon, producing MVFR ceiling and

visibility. Showers should scatter out late afternoon, and with

low confidence on clearing trends into the evening kept BKN MVFR

ceilings in the forecast.



25



&&



.ILX WATCHES/WARNINGS/ADVISORIES...

None.

&&



$$