Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 242341 AFDAKQ AREA FORECAST DISCUSSION National Weather Service Wakefield VA 641 PM EST Fri Jan 24 2020 .SYNOPSIS... Low pressure and an associated cold front track across the region tonight into Saturday morning. High pressure builds in for the end of the weekend. Another area of weak low pressure potentially tracks across the area on Monday. && .NEAR TERM /THROUGH SATURDAY/... As of 640 PM EST Friday... Early evening weather analysis shows an upper trough stretching from south-central Canada SSE to the Lower Mississippi River Valley. A well-defined upper low was slowly moving eastward over IL/IN. At the surface, ~1010 mb low pressure was centered over nrn IL/IN, with a trailing cold front stretching southward into WV, western VA/NC, and GA. Latest radar mosaic shows the main area of showers (ahead of the trailing cold front) now advancing through SW VA and entering the Piedmont of NC with scattered showers reaching our western FA. The main area of pcpn will likely remain W of the CWA until late evening. A secondary triple point low is progged to develop over the western Carolinas before tracking to the northeast across our CWA overnight. This happens as the aforementioned upper low tracks ENE toward the srn Great Lakes. Timing of the main line of convection looks to be around 03z/10 PM across the Piedmont, 07-10z/2-5 AM for the I-95 corridor (including the RIC metro), and 10-16z/5-11 AM for the VA peninsula and MD/VA/NC coastal areas. Winds slowly veer to the SE then S tonight as the secondary triple point low approaches our CWA. This will allow temperatures to warm into the mid 50s-near 60F E of I-95 during the latter half of the night (prior to the arrival of the main line of showers). Still looking like there will be some elevated instability as the line of showers moves across the area. In addition, kinematic fields are fairly robust (as is often the case during the cool season). A 50 kt southerly 925 mb jet is progged to be over ern portions of the area overnight-Sat AM while the mid-level flow will be out of the SSW-SW at 50-70 kt. The one factor that will likely keep this line from producing severe wx is the fact that surface-based instability will be non-existent across the area (as temperatures will struggle to reach 60F...with dew points likely no higher than the mid 50s in most areas). Nevertheless, any of the stronger showers could produce wind gusts of ~40 mph (highest chances across the SE). This is in line w/ the convective outlook from the Storm Prediction Center, which has our area in general thunder (w/ a marginal risk to our south). Still expecting very little in the way of thunder w/ this line as any convection will be fairly shallow. However, cannot rule out a rumble of thunder or two across NE NC. While rainfall rates will be fairly impressive for late January, the line will be moving quick enough that flooding should not be a concern, outside of nuisance poor drainage areas. Highest rainfall totals will be out to the west with totals decreasing as you head southeast. Expect 1-1.25" west of I-95, 0.75-1.0" from the Richmond metro up to the Lower MD Eastern Shore, and ~0.5" for NE NC and the Tidewater area. The cold front associated with the low clears the area by midday Saturday. Despite the frontal passage, Saturday will remain mild with high temps ranging from the mid 50s NW to low 60s across the SE. Cannot rule out some re-development of showers across the VA Northern Neck/Lower Ern Shore Sat aftn as temperatures rapidly cool aloft (as the upper trough axis approaches the region), but any remaining showers should dissipate during the evening hours. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... As of 330 PM EST Friday... High pressure builds to our SW Saturday night before weakening and moving offshore on Sunday. Slightly cooler/drier air will filter in from the W, but temperatures are expected to remain at or just above seasonal averages. Lows Saturday night will be in the low-mid 30s in most areas, with highs in the upper 40s-low 50s on Sunday. Models have come into better agreement that an upper-level shortwave will track from the TN Valley to northeast North Carolina from Monday-Monday night. While this system will be lacking moisture, models have some light QPF across the southern half of the CWA on Monday. 12z/24 EPS probabilities of at least 0.1" from 00z Mon-00z Tue are 30-40% across srn VA/NE NC. Therefore, went ahead and added slight chc PoPs across central/srn zones on Monday. These PoPs may need to be trended upward over the next day or two if the models continue to trend wetter on Monday. Temperatures will start out in the 30s Monday morning with highs warming into the upper 40s-around 50F. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... As of 330 PM EST Friday... A weak shortwave moves through the southern portion of the CWA late Monday night into early Tuesday bringing with it a slight chance of a few scattered rain showers before sunrise. High pressure moves in Tuesday and persists into Wednesday evening. A coastal low moves NE off the Carolina coastline well offshore on Thursday. There is high uncertainty with this system as to whether or not it will be close enough to produce precipitation for the CWA. The Euro is the least aggressive, the GFS the most, and the CMC a mixture of the two. As such have kept PoPs at 10-25%. High pressure once again moves into the region Friday and will persist until early Saturday. Temperatures will be near seasonal through the period. Lows Tuesday- Friday morning will range from the upper 20s in the NW to the low- mid 30s in the SE. Lows on Saturday morning will be slightly warmer with low 30s in the NW and low 40s in the SE. Highs will range from the mid-upper 40s Tuesday and Thursday, low-mid 40s on Wednesday (with the Ern Shore being the coldest in the low 40s), and from the upper 40s in the NW to lower 50s in the SE Friday. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... As of 640 PM EST Friday... VFR conditions are expected to prevail through late this evening (03z). Low pressure and an associated cold front will approach the terminals tonight before moving east of the area by midday Saturday. Ahead of the front, a line of SHRAs (w/ moderate-heavy RA) will cross the terminals from west to east. Rain should only last a few hours in any given location. Timing of the SHRAs looks to be from 06-11z at RIC, 09-14z at PHF/ORF/ECG, and 11-15z at SBY. Periods of degraded flight conditions are expected, especially during periods of moderate to heavy rain. During the rain, VSBYs will be MVFR/IFR, while CIGs will mainly be MVFR. Could see some brief wind gusts to around 30 kt with the strongest SHRAs (best chc at ORF/ECG). In addition, winds in the 1-2k ft layer may approach LLWS thresholds at SBY late tonight-Sat AM, with lesser chances at RIC/PHF. Conditions should improve quickly behind the passage of the cold front Saturday morning. Could see a shower or two re-develop near SBY Saturday aftn, but confidence in this is low-moderate. Winds veer to the SE-S tonight and may gust to ~20 kt, (especially near the coast) before becoming SW-W at 5-10 kt on Saturday. High pressure then builds in from Saturday evening- Sunday, with mainly VFR conditions expected at all TAF sites. && .MARINE... As of 330 PM EST Friday... Departing surface ridge centered between Maine and the Canadian Maritimes continues away from the region this evening as deep closed low aloft makes progress toward the area from the west. Easterly winds ~5-15 knots are in place across the marine zones this afternoon with a few gusts to 20 knots noted at elevated sensors along the eastern shore of the Ches bay. Waves are 1-2 feet with seas ranging from 3-6 ft. Secondary surface low pressure will form over the western Carolinas/Virginia tonight and cross the waters through early Saturday afternoon. The pressure gradient will tighten ahead of the low/cold front with winds increasing to 15-20 knots with gusts to 25 knots. Waves/seas build further tonight with the persistent easterly flow, and by Sat morning expect 2-4 ft waves in the Bay and seas 5-8 ft. Cold front associated with the low pressure system crosses the area waters Sat morning into early Sat aftn. Westerly flow expected after the frontal passage. SCAs are currently in effect for all coastal waters this afternoon, then spread into the Bay, lower James, and Currituck Sound late this evening through Sat AM. Pressure rises are fairly minimal Sat aftn/Sat night/Sun as the sfc high builds in from the Gulf coast as low pressure lingers well off to our N. Not much in the way of any cold air advection either, so overall do not anticipate needing any headlines after Sat AM other than for lingering seas on the coastal waters due to swell and dominant periods of 9 sec or greater into Sun AM. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 1 PM EST Saturday for ANZ634. Small Craft Advisory until 10 AM EST Saturday for ANZ630>632. Small Craft Advisory from 1 AM to 10 AM EST Saturday for ANZ633. Small Craft Advisory from 10 PM this evening to 10 AM EST Saturday for ANZ638. Small Craft Advisory until 6 AM EST Sunday for ANZ650-652-654- 656-658. && $$ SYNOPSIS...CMF/ERI NEAR TERM...ERI SHORT TERM...CMF/ERI LONG TERM...RMM AVIATION...ERI/JDM MARINE...LKB/RHR

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