Marine Weather and Tide Forecast for Grundy, VA

NEAR TERM /THROUGH WEDNESDAY/
As of 730 PM Tuesday...

High pressure centered over the Great Lakes will provide cold air advection tonight, bringing low temperatures into the mid to upper 40s. Expect the lower atmosphere to decouple allowing for calm winds and strong radiational cooling. These conditions will likely produce steam dense fog along relatively warmer river waters (54F to 62F) overnight into Wednesday morning. Any fog or low status that manage to develop will break up into low level cu field Wednesday morning before dissipating by early afternoon.
Rest of forecast remains on track.

As of 100 PM Tuesday...

Widespread low stratocumulus and stratus across WV, behind a surge of low level cold advection, will continue to lift and break up into a low cumulus field this afternoon, much like the status quo over the rest of the area. These clouds will become increasingly confined to areas in and near the mountains tonight, only to reaffirm control Wednesday morning, behind a dry cold front. These clouds will again lift and break up into a low cumulus fields Wednesday afternoon, revealing a mid deck associated with a mid/upper-level flat wave driving the morning front through.

Temperatures were suppressed by the low clouds today, but should still bottom out around normal tonight, similar to lows this morning in most locations. Highs Wednesday will again be close to normal and within a few degrees of highs today, the cooler air counteracting some increase in sunshine versus today.

SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/
As of 100 PM Tuesday...

Canadian high pressure builds over the area this period, with very dry air bringing mainly clear sky. It will also be cooler, with lows below normal Wednesday night and especially Thursday night. Highs Thursday will be a bit below normal, in the mid to upper 60s across the lowlands and 50s to low 60s over the higher terrain.

Lows Wednesday nigh will be in the mid to upper 30s across the north, lowest in the better sheltered mountain valleys, where frost is likely. With the high directly overhead Thursday night, radiational cooling conditions will be most ideal, with lows in the 30s throughout the area, and as low as the low 30s in the better sheltered mountain valleys, where frost will occur and a freeze is even possible. Low spots out across the northern and central lowlands, and valleys within the central and southern mountains, could also have frost come early Friday morning.

Frost and even freeze headlines will most likely be warranted during those time frames if this forecast trend holds, so will continue to monitor the extent of possible affected counties over the next few forecast cycles.

The very dry air will also lead to minimum relative humidity percentages in the 30s Thursday afternoon, even the 20s in spots. However, high pressure just north of the area will keep surface winds light, reducing the risk of fire spread.

LONG TERM /FRIDAY THROUGH TUESDAY/
As of 100 PM Tuesday...

Ridging shifts east of the area at all levels Friday through Saturday, allowing a full-lattitude mid/upper-level trough to approach from the west. That trough will drive a surface cold front through the area on Sunday, before crossing itself Sunday afternoon and night. Models are still divergent on the exodus of this mid/upper-level trough Sunday night and Monday, the more progressive Canadian still allowing mid/upper-level ridging to build from the west on Monday, while the ECMWF and especially the GFS slow the feature down and close off a mid/upper-level low over the northeastern states.

After a continuation of dry weather, with a stout warming trend, Friday and Saturday, the amplified system is likely to pull enough Gulf moisture northward ahead of it for showers Saturday night through Sunday night. This timing is likely to be better resolved in future forecasts, but the showers are most likely during the day on Sunday.

There could be a thunderstorm in the middle Ohio Valley Saturday evening if the front, or at least a lead surface trough, gets close enough. By contrast, there could be a thunderstorm Sunday afternoon if the front is slow enough to allow sufficient diurnal heating ahead of it, the amplified system somewhat offsetting the lowering autumn sun angle.
Central guidance seems to split the difference, with the slight chance for a thunderstorm Saturday evening and Sunday afternoon.

The Storm Prediction Center carries a Slick Risk level 15 percent chance for severe thunderstorms within 25 miles of a point well upstream, across the mid Mississippi Valley, for Day 5, Saturday and Saturday night. In tandem, the Weather Prediction center carries a Marginal Risk level 5 percent chance for excessive rainfall within 25 miles of a point well upstream, across a smaller portion of the mid Mississippi River Valley but a bit farther up the lower Ohio River Valley, for Day 5, Saturday and Saturday night. Believe the early timing and progressive nature of the system should mitigate these concerns, respectively, for the forecast area on Day 6, Sunday.

The end of the forecast period vaguely resembles the restoration of dry weather, with Monday bringing drying and clearing given a more progressive solution, or clouds and even the chance for showers given a slower, more amplified mid/upper-level trough and possibly even a secondary cold front. Central guidance portrays a slight chance for showers Monday morning lifting quickly northeast during the day.

Temperatures climb above normal Friday through Saturday night ahead of the incoming system, and then back down to and below behind it early next week. Relative humidity percentages will drop down to the 20s and 30s Friday afternoon. However, flow will again be light, reducing the risk of fire spread. Flow will increase a bit from the south on Saturday, but so should dew points and, albeit to a lesser extent given the higher high temperatures, minimum afternoon relative humidity percentages.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/
As of 730 PM Tuesday...

A large area of low stratus will continue to erode across the western foothills, as drier airmass filters in across the lowlands. Expect IFR/MVFR ceilings at BKW at the beginning of the period, lifting to MVFR/VFR by midnight. MVFR ceilings at EKN will lift from MVFR to VFR by midnight. The rest of the area will enjoy clear skies and widespread VFR conditions at least through 06Z.

A high pressure, centered over the Great Lakes, will keep northerly flow across the area through at least Wednesday. Cold advection will continue to bring fresher airmass to the area.
Cold air over relatively warmer river waters (54F to 62F) will produce steam dense fog along river valleys, under clear skies.
Winds aloft around 15 knots should not impede dense fog from develop as it was the case last night. Any IFR/LIFR conditions due to fog or low stratus that manage to develop will break up into MVFR/VFR low cu field by 15-16Z Wednesday morning.

Light northerly flow will become calm tonight as the lower atmosphere decouples.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z THURSDAY...

FORECAST CONFIDENCE: Medium.

ALTERNATE SCENARIOS: Improvement on ceilings this evening at BKW and EKN may vary from forecast.

EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.

UTC 1HRLY 21 22 23 00 01 02 03 04 05 06 07 08 EDT 1HRLY 17 18 19 20 21 22 23 00 01 02 03 04 CRW CONSISTENCY M M M M M M M M M M M H HTS CONSISTENCY M M M H H H H H H H M M BKW CONSISTENCY H M L H M M M M M L L L EKN CONSISTENCY M H H M M M M M M M M M PKB CONSISTENCY M M H H H H H H H H M M CKB CONSISTENCY H M M M M M M M M M M M

AFTER 00Z THURSDAY...
Patchy IFR river valley fog is possible each morning for the rest of this week.

RLX WATCHES/WARNINGS/ADVISORIES
WV...None.
OH...None.
KY...None.
VA...None.