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FXUS61 KRNK 020648 AFDRNK

Area Forecast Discussion National Weather Service Blacksburg VA 248 AM EDT Thu May 2 2024

SYNOPSIS
Today and tonight high pressure result in dry weather and above normal temperatures. A low pressure system brings wet weather to the region by the weekend along with cooler temperatures.
Unseasonably warm temperatures and a daily threat of late day showers and thunderstorms return for Monday through Wednesday.

NEAR TERM /THROUGH TONIGHT/
As of 245 AM EDT Thursday...

Key message:

- Unseasonably warm today - Fog in the piedmont this morning

Region remains under a 500 mb ridge today and tonight. Little variation in the synoptic pattern between models. No change in airmass today with 850 mb temperatures in the +14 to +18 range by the end of the day. Expect high temperatures in most locations to be 10 to 20 degrees above normal.

Nighttime fog satellite images were showing the formation of fog in central and eastern Virginia, and along the New and Greenbrier River Valleys. Similar to Wednesday, any fog will dissipate by mid morning.

Mid and high clouds spread into the area tonight. NBM lows are reasonable.

SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/
As of 125 AM EDT Thursday...

Key Points:

1. Above normal temperatures with Friday the warmest day.
2. Chance of showers and storms each day with Saturday having the highest probability.
3. Locally heavy rain is possible Saturday and Saturday evening.

A look at the 1 May 00Z NCEP Ensemble Mean 500 mb Geopotential heights shows on Friday a N-S oriented upper ridge centered from western NY south into eastern NC. An eastward moving closed low will progress from Manitoba to Ontario. On Saturday, the ridge shifts a bit farther east while a negatively tilted shortwave trough moves through the Great Lakes region. There is a hint of a weak shortwave trough moving across GA/FL. On Sunday, the Great Lakes trough is a bit less amplified and extends south from Ontario into the mid-Atlantic states. The GA/FL shortwave trough will be closer to the SC/GA border. At the surface, on Friday a ridge of high pressure will extend N-S just off the East Coast of the US. Low pressure will be over southwest Ontario with a general area of troughiness extending southeast into the Ohio and Tennessee Valleys.
This pattern changes very little on Saturday. By Sunday, the ridge is expected to have shifted a bit more east while the trough shifts east to over our region.

Output from the 1 May 12Z Ensemble Situational Awareness Table shows 850mb temperatures lower than those expected today, but still above normal for this time of the year for Friday. Additionally, at values of +13C to +14C they touch the low end of the 90 to 97.5 percentile of the thirty-year percentile of climatology. On Saturday and Sunday, values are only slightly cooler at +12C to +13C.
Precipitable Water values on Friday are expected to range from 1.00 to 1.25 inches, with the upper portion of this range touching the 90 to 97.5 percentile of the thirty-year climatology. On Saturday, these numbers increase to 1.25 to 1.50 inches, or with the 90 to 99 percentile of the thirty-year climatology. By Sunday, values are expected to decrease slightly to 1.00 to 1.25 inch.

The above weather scenario continues to offer the region with a forecast that has well above normal temperatures for this time of the year, with Friday being the warmest of the three days.
Precipitation chances look to increase through Saturday thanks to both improving onshore moisture flux within the clockwise flow of the exiting ridge, and increased dynamics aloft with the approach of the upper trough and approach and passage of the surface front. The concern exists Saturday into Saturday evening for locally heavy rain. While we are not expecting a widespread heavy rain evening, the training of excessive moisture laden showers and storms could result in localized rainfall amounts over one inch in a short period of time. Sunday is a bit of a question mark. Much will depend upon how much progress the front makes after Saturday and whether a shortwave trough moving through the Deep South interacts with the front. Our forecast has been banking on the front lingering over or near the region, helping to maintain a focus for additional activity on Sunday. At this time, we see not reason to deviate notably from that solution.

Confidence in the above weather pattern is moderate.

LONG TERM /MONDAY THROUGH WEDNESDAY/
As of 100 AM EDT Thursday...

Key Points:

1. Trending warmer each day with Wednesday potentially the warmest.
2. Chance of showers/storms each day, especially northwestern sections, with Monday seeing the best coverage.

A look at the 1 May 00Z NCEP Ensemble Mean 500 mb Geopotential heights shows zonal flow across our area with a shortwave trough moving through the Canadian Maritimes on Monday. An amplified trough is expected to dig even more across the the Pacific Northwest and the Rockies. Thanks to the deepening trough, ridging is expected to develop from the mid-Mississippi Valley north into southern Manitoba. On Tuesday, the axis of the ridge shift east to over our region, while a broad trough covers much of western CONUS. By Wednesday, perhaps due to ensemble averaging, both the trough and the ridge lose a lot of their definition with a lengthly path of sw- ne flow from the Four Corners region through the mid-Mississippi Valley to across our region and into the Western Atlantic. At the surface, on Monday, low pressure deepens over the Dakotas with a cold front extending south into Texas. A shortwave trough will be heading northeast through New England and the Canadian Maritimes. On Tuesday, the low over the Dakotas makes limited progression eastward. Southwest flow develops over area between this low and an area of high pressure in the Western Atlantic off the GA/FL coast. On Wednesday, the main low makes some progress eastward to over the Upper Mississippi Valley. There are hints a shortwave trough may ride northeast over our region within the southwest flow.

Output from the 1 May 12Z Ensemble Situational Awareness Table shows 850mb temperatures for Monday of +12C to +14C, around +16C on Tuesday, or within the 90 to 97.5 percent of the thirty-year climatology. For Wednesday, we could be looking temps around +18C, or numbers that would be the very warmest among the thirty-year climatology for this time of the year. Precipitable Water values on Monday are expected to average 1.00 to 1.25 inches. These values increase to around 1.25 inches on Tuesday, which touches the 90 to 97.5 percentile of the thirty-year climatology, and for Wednesday, values are down slightly to the 1.00 to 1.25 range.

The above weather scenario offers the region a three day period with gradually increasing temperatures. Values on Wednesday have the potential of being the warmest of the three. As we transition into a southwest flow pattern with the main low over the Northern Plains states, we will have the potential for shortwave troughs within this flow regime to pass over or just north of the area. Each day of the forecast will have a chance of showers or storms for a portion of the region, with the northwestern sections being the favored location because of the aforementioned pattern. Monday has the potential of for having greatest potential for showers/storms for a greater expanse of the area as the Saturday/Sunday cold front lifts back north as a warm front.

Confidence in the above weather pattern is moderate.

AVIATION /07Z THURSDAY THROUGH MONDAY/
As of 145 AM EDT Thursday...

Satellite Fog images showed fog developing in central and eastern Virginia. visibility will lower to MVFR at KLYH and KDAN after 08Z/4AM. Bufkit forecast sounding suggest the western edge of the more extensive fog this morning will be somewhere between KFVX and KDAN/KLYH. What fog does form will dissipate by 14Z/10AM.

VFR conditions are expected for the rest of the TAF forecast period.

Once mixing begins today winds will be mainly from the southeast to southwest with speeds less than 10 kts.

Above average confidence for ceiling and wind.
Average confidence for the extent of fog this morning.

Extended Aviation Outlook...

Thursday night and the first half of Friday look VFR with dry weather.

A frontal showers and TSRA to the region, possibly as early as Friday afternoon in the west. This timing could easily be slowed down however.

The increased chances for rain spreads to the remainder by sometime Saturday along with more extensive MVFR ceilings.

Chances for rain/TSRA/MVFR or lower conditions continue Sunday through Monday, mainly in the afternoon hours each day.

CLIMATE
As of 200 PM EDT Wednesday...

Record high temperatures for May 2

Bluefield, WV....89 in 2010 Danville, VA.....93 in 1942 Lynchburg, VA....91 in 1942 Roanoke, VA......92 in 1959 Blacksburg, VA...87 in 1942

RNK WATCHES/WARNINGS/ADVISORIES
VA...None.
NC...None.
WV...None.

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