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Area Forecast Discussion (AFD)

Issued by Charleston, SC (CHS)

FXUS62 KCHS 221459

Area Forecast Discussion
National Weather Service Charleston SC
1059 AM EDT Fri Mar 22 2019

High pressure will build over the region through the weekend.
Low pressure may move across the region on Monday night through
Tuesday night. High pressure will then rebuild. 


Today: West-northwest flow will persist across the Southeast United 
States along the southern periphery of a large mid/upper lvl trough 
of low pressure centered over the Northeast. At the sfc, high 
pressure centered over the Mississippi Valley will gradually shift 
east as low pressure deepens off the Northeast coast. Given the 
setup, northwest winds late this morning will become more directly 
west this afternoon, helping advect dry air over the region and 
maintaining clear skies. Temps should peak in the upper 60s across 
the Tri-County area to lower 70s across lower Southeast South 
Carolina and Southeast Georgia. These temps should produce a fair 
amount of low-lvl mixing this afternoon, leading to breezy westerly 
winds topping out in the 20-25 mph range. The combination of these 
winds and RH values dipping into the 20-25% range could produce an 
elevated risk of fire weather this afternoon (see fire weather 
section below).  

Tonight: High pressure over the Upper Midwest will become the 
dominant feature, veering winds around to more northerly late 
tonight behind a passing front. Clear skies and a dry forecast will 
prevail. Lows are forecast to reach the low to mid 40s in most areas 
away from the beaches.


High pressure over the area on Saturday will slide off the 
Carolina coast on Sunday. Dry weather with warming temperatures 
are expected. Highs Sunday will be in the mid to upper 70s.

An upper shortwave will approach the area on Monday, pushing a 
surface low pressure system into central and eastern SC during 
the afternoon. 0-6 km flow will be predominantly westerly so 
moisture return ahead of the low will be somewhat limited. 
Isolated to scattered showers should move into the area late 
Monday afternoon. There may be enough instability to support a 
few thunderstorms as well. Strong warm advection will result in 
another warm day with highs in the upper 70s.


A series of shortwaves will move through the area Monday night 
through Tuesday night while a backdoor cold front slowly sinks 
south through the area. We currently have the highest rain 
chances on Tuesday as this coincides with the front dropping 
through the area and the strongest PVA aloft. Cool high pressure
will affect the area through Wednesday before weakening and 
shifting east, allowing for a warming trend late next week.


VFR conditions will prevail at both KCHS and KSAV through 12Z 
Saturday. Westerly winds will become gusty late this morning and
this afternoon, with frequent gusts into the 20-25 knot range. 

Extended Aviation: Flight restrictions possible Monday night 
through Tuesday night.


Today through Tonight: Northwest winds topping out in the 15-20 knot 
range will prevail late this morning and any lingering Small Craft 
Advisories are expected to come down by noon as seas gradually 
subside. Winds will see a brief west-southwesterly surge this 
afternoon, and could be near advisory thresholds for Charleston 
Harbor and the Charleston County waters. Overall, winds should
top out in the 15-20 knot range with seas 2-4 feet out to 20 nm
and 4-5 feet beyond this afternoon. Overnight, winds will veer
around to northerly after midnight. Winds will remain elevated
in the 15-20 knot range and just below advisory thresholds. 

High pressure will maintain relatively benign marine conditions
Saturday through Sunday night. Stronger southwest flow will 
setup on Monday ahead of a low pressure system, though the 
current forecast keeps conditions just below advisory levels.

A strong northeast gradient will develop next Tuesday through 
Thursday behind the backdoor cold front. Small Craft Advisories 
are likely across most of the marine area.

Rip Currents: Breezy westerly winds and moderate swell energy
will combine to produce a moderate risk of rip currents at all
beaches through this evening.


Today: High pressure will build into the area as low pressure off 
the New England coast deepens. Dry air across the region will result 
in relative humidity values falling into the 20-25 percent range 
this afternoon. Westerly winds will also be breezy this afternoon, 
with frequent gusts into the 20-25 mph range. Given the conditions 
along with coordination with users/partners and surrounding NWS 
offices, a Fire Danger Statement has now been issued for all of 
Southeast Georgia and Southeast South Carolina until 8 PM.

Saturday through Sunday: Critical or near-critical relative
humidity values are likely to persist.


KCLX has returned to service. However, the radar will remain in 
clear air mode, VCP32, until Monday. Parts are on order.


MARINE...Small Craft Advisory until noon EDT today for AMZ374.