####018006869#### FXUS61 KGYX 041656 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1256 PM EDT Sat May 4 2024 .SYNOPSIS... High pressure near the coast will provide dry conditions through today, with increasing onshore flow and humidity. Thickening clouds, cooler temperatures, and rain showers are expected by Sunday as a frontal system approaches New England. Clearing is likely not coming until Monday behind a cold front. Warmer and sunnier conditions are expected into Tuesday, then more unsettled weather returns around the middle of next week. && .NEAR TERM /UNTIL 7 PM THIS EVENING/... 100 PM Update... A weak vorticity maximum is crossing over northern areas and this is allowing for a few widely scattered showers to develop, as seen on latest radar imagery and area webcams. This vort max will continue to sink southeastward through the afternoon and therefore added some low end slight- chance PoPs to account for this. Otherwise, no significant changes were made to the forecast. Previously... 1030 AM Update... Minor changes to reflect latest observational trends. Northeast radar mosaic continues to show weak returns moving southeastward over southern NH but thus far there haven't been any MPING or ASOS reports of this activity reaching the ground. This is likely due in part to low mid-level RH, as seen on the 12Z KGYX RAOB report. Previously... 648 AM Update...Quick tune up of sky coverage this morning, along with temperature trends through the dawn hours. Little change otherwise. Previously... An upper level ridge moves toward the East Coast while surface high pressure centered near Labrador this morning builds south into the Gulf of Maine today... resulting in another fair weather day, albeit with increasing onshore flow and associated clouds. Signs of increasing low- and mid- level moisture associated with this trend are evident even this morning as patchy ground fog has developed in most places... and a mid- level stratus deck has built over portions of the foothills, where humid NE mid- level flow is dammed against the mountains. The trend for today will be to mix out low clouds and fog initially... but build back some stratocu by the afternoon, mainly over the interior of Maine beneath mixed cirrus decks. The ridge overhead will keep us dry, however it will be cooler than yesterday especially at the coast where temperatures may not or may just barely make it out of the 40s. The warmest and sunniest spots will likely be in the Connecticut and Lower Merrimack River Valleys, with highs in the mid-60s. && .SHORT TERM /7 PM THIS EVENING THROUGH SUNDAY NIGHT/... High pressure extending offshore of the Maritimes combined with an approaching cold front from the Great Lakes continues to support southeast flow off the Gulf of Maine... with low clouds filling into an overcast sky for most places tonight, except for the upper Connecticut River Valley which benefits from the Whites blocking humid onshore flow. Some fog and drizzle are likely to develop too, mainly in southern New Hampshire into southwest Maine where low- level humidity will be at its highest. One of the bigger questions for Sunday will be how efficiently we'll be able to mix out low stratus, if at all, before a pre- frontal trough brings a moisture axis and associated rainfall across the region. Model trends have been fairly steady with this wave delivering about 0.2-0.4" for most places... locally higher, lower elsewhere... Sunday afternoon and overnight. While ceilings are forecast to lift a bit during the day, hires guidance coming into view suggests a fair amount of overcast to persist. Thus between clouds and onshore flow, temperatures will be limited to the low- or mid-50s... or 40s, nearby to the coast and if ceilings remain low. A building southeasterly breeze will make conditions feel a bit more raw as well. Rain will exit east Sunday night with drier air pushing in aloft, however at the surface conditions will remain humid with fog and low ceilings likely. Winds will gradually pull more southerly and southwesterly, which will at least cut some of the maritime influence down by Monday. && .LONG TERM /MONDAY THROUGH SATURDAY/... Overview: Unsettled weather expected until a cold front passes Monday morning. High pressure and warm temperatures arrive the latter part of Monday, continuing into Tuesday. Additional unsettled weather is expected mid to late week as broad low pressure moves into the eastern Great Lakes. Details:Perhaps some remaining drizzle along the coast early Monday morning, but drying across the CWA should be underway by mid morning. NW breeze will also kick up to enhance drying through the afternoon. Should this stay on track, temperatures will be in for a rebound later in the day with highs in the 70s possible for southern NH and into southern Maine's interior. Tuesday follows up as warm and dry, before another period of unsettled weather for mid to late week. Current NBM PoPs are likely overdone due to the wide spread of guidance solutions, and have tried to emphasize this uncertainty by keeping just a chance of rain to close out the week. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... Short Term...Spotty/low confidence IFR/LIFR in FG possible this morning... clearing to VFR today with increasing light SE or E flow. Brief MVFR decks possible for interior ME (AUG) this afternoon. Widespread restrictions expected to develop tonight... with MVFR/IFR VSBY, CIGs except at KHIE which likely remains VFR. Some improvement possible on Sun, however increasing RA chances bring restrictions again during afternoon/evening. Low CIGs, possibly low VSBY persist at least along the coast into early Mon. Long Term...Ceilings should improve to VFR at all terminals into Monday afternoon through Tuesday. Unsettled weather likely brings more restrictions from mid-week, onward. && .MARINE... Short Term...NE flow 10-20 kts today turns SE by early Sunday with increasing potential for fog, then rain later in the day and overnight into early Monday. A few gusts near 25 kts are possible, with waves 3-5 ft, though conditions will remain predominantly below SCA thresholds. Long Term...The cold front will pass over the waters Monday morning, bringing better vis conditions through Tuesday. Conditions should remain below SCA criteria with the frontal passage through at least Wednesday. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Tubbs ####018006157#### FXUS65 KTFX 041658 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 1058 AM MDT Sat May 4 2024 ...Aviation Section Updated... .SYNOPSIS... Weak high pressure will keep North Central, Central, and Southwest Montana dry and a bit warmer than normal through tonight with gusty southeasterly winds. However, a Pacific weather system will first bring an increasing chance for showers and thunderstorms to the area on Sunday, then more widespread mountain snow and low elevation rain with cooler than normal temperatures Monday through Thursday. Warmer and drier conditions should then move in to end the week. && .UPDATE... No major changes were made to the forecast on this quiet morning. Expect clouds to be on the increase today, along with some breezy areas across the plains. Ludwig && .AVIATION... 1058 AM MDT Sat May 4 2024 (04/18Z TAF Period) VFR conditions will prevail through much of the 0418/0518 TAF period before lowering CIGS and increasing chances for precipitation bring MVFR/low-VFR conditions to the terminals of Southwest Montana (i.e. KWYS, KEKS, and KBZN) beyond 12z Sunday. Prior to 12z Sunday, mid- to upper level cloudiness will begin to overspread the Northern Rockies from southwest to northeast; however, mountain obscuration will generally be confined to the Continental Divide. Otherwise, easterly surface winds will begin to increase during the late afternoon/early evening hours over the plains of Central and North Central Montana, especially at the KHVR and KLWT terminals. - Moldan Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PREV DISCUSSION... /ISSUED 520 AM MDT Sat May 4 2024/ Today and Tonight... High pressure aloft will keep this period dry and a bit warmer than normal across North Central, Central, and Southwest Montana. However, a cold front approaching Montana from the west ahead of a Pacific low pressure system will combine with an exiting area of surface high pressure to strengthen the surface pressure gradient over the area. This is forecast to bring southerly winds gusting in excess of 30 mph at times today across the area, with the winds shifting more easterly tonight and remaining gusty. Sunday through Sunday Night... The Pacific system is forecast to move east across the Great Basin on Sunday, which put the area under an increasingly moist and unstable southerly flow aloft as the Pacific cold front moves across the area. This should spread showers over most of the area Sunday into Sunday evening with a few embedded thunderstorms. The main threats from these storms will be isolated lightning strikes, brief heavy rain showers, and gusty winds, but some small hail is also possible. The main threat for thunderstorms will diminish during the evening, but snow levels will start to lower from the southwest overnight as the low pressure area is forecast to move northeast into Southwest Montana. This will likely result in at least some light accumulations of wet snow above 6000 feet, which may cause some travel problems over mountain passes, so some winter weather highlights may be needed starting Sunday night in Southwest Montana. Monday through Thursday... This is forecast to be coolest, wettest, and windiest period of the upcoming week. The low pressure center is predicted to continue moving northeast to around the Montana/North Dakota border Monday into Monday night, where it seems to deepen and cut off from its main trough, causing it to remain there into Wednesday. This will result in deep moisture wrapping around the low and bringing widespread mountain snow and low elevation rain to the forecast area, as temperatures cool back below normal. The heaviest precipitation amounts are forecast to be closest to the low pressure center, which includes the plains of North Central Montana; probabilistic guidance gives a 50 to 70 percent chance of at least 1 inch of precipitation there for Monday through Wednesday night, with a 40 to 50 percent chance of 2 inches of precipitation across Hill, Blaine, and Chouteau Counties. However, this same guidance gives at least a 50 percent chance of 12 inches or more of snow to the mountains of the Rocky Mountain Front, the Little and Big Belt mountains of Central Montana, and the mountains of Gallatin and Madison Counties; in fact, there is a 70+ percent chance of 24 inches or more of snow in the Little Belts. In addition, models are forecasting that northwest winds moving around the low pressure area at the mid levels of the atmosphere could exceed 60 mph on Tuesday, which may translate down into at least the mountains, if not the plains of North Central Montana, mainly on Tuesday. Overall, confidence is increasing in the potential need for winter weather highlights in the mountains and wind highlights on the plains. However, run-to- run model inconsistency adds uncertainty to timing and location for such highlights, so will hold off for now. Overall, though, the system should start exiting the area on Thursday. Friday through next Saturday... Ensemble model clusters are in good agreement with bringing high pressure into Montana late in the week, but just how strong it will be, and just how warm the temperatures will be, remains uncertain. Regardless, this should bring drying conditions to the area with a return to warmer than normal temperatures. -Coulston && .PRELIMINARY POINT TEMPS/POPS... GTF 63 42 64 42 / 0 10 30 90 CTB 58 37 59 40 / 0 10 20 30 HLN 67 44 68 43 / 10 10 60 80 BZN 65 41 66 36 / 0 10 70 80 WYS 59 36 53 28 / 0 30 90 90 DLN 64 44 60 36 / 0 20 70 90 HVR 63 39 70 43 / 0 0 10 80 LWT 58 36 66 39 / 0 0 20 80 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls